Light-emitting device, liquid-crystal display device and method for manufacturing same

ABSTRACT

The present invention provides a structure of a semiconductor device that realizes low power consumption even where increased in screen size, and a method for manufacturing the same. The invention forms an insulating layer, forms a buried interconnection (of Cu, Au, Ag, Ni, Cr, Pd, Rh, Sn, Pb or an alloy thereof) in the insulating layer. Furthermore, after planarizing the surface of the insulating layer, a metal protection film (Ti, TiN, Ta, TaN or the like) is formed in an exposed part. By using the buried interconnection in part of various lines (gate line, source line, power supply line, common line and the like) for a light-emitting device or liquid crystal display device, line resistance is decreased.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The present invention relates to a semiconductor device having a circuitconfigured with thin-film transistors (hereinafter, referred to as TFTs)and a method for manufacturing same. For example, the invention relatesto an electronic apparatus mounting, as a part, an electro-opticaldevice represented by a liquid-crystal display or a light-emittingdevice having OLEDs.

Incidentally, the semiconductor device in this description refers to adevice as a whole which is capable of functioning by the utilization ofa semiconductor characteristic, i.e. electro-optical devices,semiconductor circuits and electronic apparatuses are all fallen undersemiconductor devices.

2. Description of the Related Art

Recently, attentions are drawn to the art to structure a thin-filmtransistor (TFT) by the use of a semiconductor film (thickness:approximately several to several hundred nm) formed over a substratehaving an insulating surface. Thin-film transistors are broadly used onelectronic devices, such as ICs and electro-optical devices.Particularly, development is hurried up for a switching element for animage display device.

Conventionally, the liquid-crystal display is known as an image displaydevice. There is a tendency of frequent use of the liquid-crystaldisplay of the active-matrix type because of the capability of obtainingan image with definition as compared to the passive-type liquid-crystaldisplay devices. In the active-matrix liquid-crystal display device, adisplay pattern is formed on the screen by driving the pixel electrodesarranged in a matrix form. Specifically, by applying a voltage tobetween a selected pixel electrode and a counter electrode correspondingto that electrode, optical modulation is done in the liquid-crystallayer arranged between the pixel electrode and the counter electrode.The optical modulation is recognized as a display pattern by theobserver.

Meanwhile, for the light-emitting devices using OLEDs, TFTs arerequisite elements in realizing active-matrix drive scheme.Consequently, the light-emitting device using OLEDs has, on each pixel,at least a TFT functioning as a switching element and a TFT supplyingcurrent to the OLED. Light-emitting elements using an organic compoundas phosphors, featured in small thickness, light weight, highresponsibility, direct-current low voltage drive, are expected for theapplication to the next-generation display panel. In particular, thedisplay device arranging the light-emitting elements in a matrix form isconsidered excellent in respect of its wide viewing angle and hencehigher visibility as compared to the conventional liquid-crystal displaydevice.

The luminescent mechanism of a light-emitting element is considered asfollows. That is, by applying a voltage to a pair of electrodessandwiching an organic compound layer, the electrons injected at thecathode and the holes injected at the anode are recombined at luminouscenters in the organic compound layer. The molecular exciter, uponretuning to the -ground state, gives off energy causing light emission.The excitation state is known as singlet excitation and tripletexcitation. Electro-luminescence is considered possible through any ofthe excitation states.

For the light-emitting device formed by such light-emitting elementsarranged in a matrix form, it is possible to use drive schemes ofpassive-matrix drive. (simple matrix type) and active-matrix drive(active-matrix type). However, in the case with increased pixel density,the active-matrix type having a switch on each pixel (or one dot) isconsidered advantageous because of the capability of driving at lowvoltage.

There are increasing applications of such active-matrix type displaydevices (representatively, liquid-crystal and light-emitting displaydevices). With the increasing area in screen size, there are increasingrequirements for improving definition, opening ratio and reliability. Atthe same time, requirements are toward production increase and costreduction.

Conventionally, where TFTs are fabricated by using aluminum as a TFTgate interconnection material, there encounter projections, such ashillocks or whiskers, formed by thermal process or TFT poor operation orTFT characteristic reduction due to the diffusion of aluminum atoms intothe channel region. To cope with this, in the case of using a metalmaterial resistive to the thermal process, representatively highmelt-point metal element, the problem arises that interconnectionresistance increases or so with increase in screen area size, incurringincreased power consumption.

Accordingly, it is a problem of the present invention to provide astructure of a semiconductor device that realizes low power consumptioneven where increased in screen size, and a method for manufacturing thesame.

SUMMARY OF THE INVENTION

In order to solve the problem, the present invention forms an insulatinglayer, forms a buried interconnection (of Cu, Au, Ag, Ni, Cr, Pd, Rh,Sn, Pb or an alloy thereof) in the insulating layer. Furthermore, afterplanarizing the surface of the insulating layer, a metal protection film(Ti, TiN, Ta, TaN or the like) is formed in an exposed part. By usingthe buried interconnection as part of various lines (gate line, sourceline, power supply line, common line and the like) of light-emittingdevices and liquid-crystal display device, line resistance is decreased.The present invention can realize low power consumption even in casescreen size is increased in area.

The structure of the invention disclosed in this description is, asexemplified in FIGS. 1A-1E, a light-emitting device comprising, betweena first substrate having an insulating surface and a second substratehaving light transmission property:

a pixel region having a plurality of light-emitting elements, the lightemitting element having a first electrode, a layer containing organiccompound provided on and in contact with the first electrode, and asecond electrode provided on and in contact with the layer containingorganic compound; and

a drive circuit having thin-film transistors;

whereby the pixel region is arranged with a gate line, source line orpower supply line made with a buried interconnection.

In the structure, the buried interconnection is of copper, silver, goldor an alloy thereof which is to be plating-processed. Also, the buriedinterconnection is provided in a layer lower than the thin-filmtransistor.

Also, in the structure, the layer containing organic compound is amaterial for white light emission and combined with a color filterprovided on the second substrate. Otherwise, the layer containingorganic compound is a material for single-color light emission andcombined with a color change layer or coloring layer provided on thesecond substrate.

Also, the structure of the invention for realizing the construction is amethod for manufacturing a light-emitting device comprising:

a first step of forming an etching-stop layer having an electricconductivity on an insulating surface;

a second step of forming a first insulating film covering theetching-stop layer;

a third step of etching the first insulating film to open an openingreaching the etching-stop layer;

a fourth step of forming a seed and carrying out plating to form aburied interconnection covering the opening;

a fifth step of carrying out planarization;

a sixth step of forming a second insulating film containing aluminum;

a seventh step of forming a third insulating film on the secondinsulating film;

an eighth step of forming a semiconductor layer on the third insulatingfilm;

a ninth step of forming a fourth insulating film on the semiconductorlayer;

a tenth step of forming agate electrode on the fourth insulating film;

an eleventh step of forming a line connecting to the semiconductor layerand a line connecting the buried interconnection;

a twelve step of forming a first electrode; and

a thirteenth step of forming a layer containing organic compound on thefirst electrode and a second electrode on the layer containing organiccompound.

Also, in the structure concerning the manufacturing method, the buriedinterconnection is a power supply line.

Also, in the structure concerning the manufacturing method, the buriedinterconnection is of copper, silver, gold or an alloy thereof.

Also, the structure of another invention is, as shown in FIG. 12, aliquid-crystal display device comprising, between a first substratehaving an insulating surface and a second substrate having lighttransmission property:

a pixel region having a first electrode, a second electrode and aliquid-crystal material sandwiched between the electrodes; and

a drive circuit having thin-film transistors;

whereby the pixel region is arranged with a gate line or source linemade by a buried interconnection.

Also, in the structure, the buried interconnection is of copper, silver,gold or an alloy thereof. Also, in the structure, the buriedinterconnection is provided in a layer lower than the thin-filmtransistor.

Also, the structure of the invention for realizing the construction is amethod for manufacturing a liquid-crystal display device comprising:

a first step of forming an etching-stop layer having an electricconductivity on an insulating surface;

a second step of forming a first insulating film covering theetching-stop layer;

a third step of etching the first insulating film to open an openingreaching the etching-stop layer;

a fourth step of forming a seed and carrying out plating to form aburied interconnection covering the opening;

a fifth step of carrying out planarization;

a sixth step of forming a second insulating film containing aluminum;

a seventh step of forming a third insulating film on the secondinsulating film;

an eighth step of forming a semiconductor layer on the third insulatingfilm;

a ninth step of forming a fourth insulating film on the semiconductorlayer;

a tenth step of forming a gate electrode on the fourth insulating film;

an eleventh step of forming a source line connected to the semiconductorlayer and a line connecting between the buried interconnection and thegate line.

Also, in the structure concerning the manufacturing method, the buriedinterconnection is a gate line. Also, in the structure concerning themanufacturing method, the buried interconnection is of copper, silver,gold or an alloy thereof.

Also, plating may be done using the etching-stop layer as a seed.

Incidentally, the light-emitting element (EL element) has a layercontaining an organic compound to obtain electro-luminescence caused byapplying an electric field (hereinafter, described as EL layer), ananode and a cathode. The electro-luminescence in an organic compoundincludes luminescence of upon returning from a singlet excitation stateto the ground state (fluorescence) and luminescence of upon returningfrom a triplet excitation state to the ground state (phosphorescence).The light-emitting device fabricated by the invention is applicable forthe case using any of luminescence.

The layer containing organic compound is in a lamination structure.Typically, included is a lamination structure having a hole transportlayer/light-emitting layer/electron transport layer on the anode. Thisstructure has an extremely high light-emission efficiency. Almost allthe light-emitting devices currently researched and developed adopt thisstructure. Besides, the structure may be a lamination of pole injectionlayer/hole transport layer/electron transport layer or hole injectionlayer/hole transport layer/light-emitting layer/light-emittinglayer/electron transport layer/electron injection layer in the order.The light-emitting layer may be doped with a fluorescent pigment or thelike. These layers may all be formed by using low-molecular materials orall be formed by using high-molecular materials. Incidentally, in thedescription, all the layers provided between the cathode and the anodeare collectively referred to as a layer containing organic compound (ELlayer). Accordingly, the hole injection layer, the hole transport layer,the light-emitting layer, the electron transport layer and the electroninjection layer are all included in the EL layer. Also, the layercontaining organic compound (EL layer) may contain an inorganic materialsuch as silicon.

Meanwhile, in the light-emitting device of the invention, there is nolimitation in drive method for screen display, i.e. dot-sequence drivemethod, line-sequence drive method or plane-sequence drive method may beused. Typically, line-sequence drive method may be used, andtime-division tone drive method or area-tone drive method be properlyemployed. Also, the video signal to be input to the source line of thelight-emitting device may be an analog signal or digital signal. Thedrive circuit or the like may be properly designed matched to the videosignal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1E are sectional views each showing a process of the presentinvention (embodiment);

FIGS. 2A and 2B are views each showing a section of a light-emittingelement of the invention (example 1);

FIG. 3 is a top view in a manufacturing process of a light-emittingdevice (example 1);

FIG. 4 is a top view in a manufacturing process of a light-emittingdevice (example 1);

FIG. 5 is a top view in a manufacturing process of a light-emittingdevice (example 1);

FIG. 6 is a top view in a manufacturing process of a light-emittingdevice (example 1);

FIGS. 7A to 7C are figures each showing a lamination structure of thelight-emitting element (example 1);

FIGS. 8A to 8C are typical figures in the case of using white emissionlight for full-color display (example 1);

FIG. 9 is a figure showing a transmissivity of a coloring layer example1);

FIG. 10 is a figure showing a chromaticity-coordinate (example 1);

FIGS. 11A and 11B are a sectional view and top view of an active-typedisplay device (example 1);

FIG. 12 is a view showing a sectional view of a liquid-crystal displaydevice (example 2);

FIG. 13 is a figure showing a top view in a manufacturing process of aliquid-crystal display device (example 2);

FIGS. 14A to 14C are views showing examples of electronic apparatuses;and

FIGS. 15A and 15B are views showing examples of electronic apparatuses.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will now be explained.

Herein, in FIGS. 1A-1E are shown an example to form a buriedinterconnection and TFT.

First, an etching-stop layer 102 is formed on a substrate 100 having aninsulating surface. The etching-stop layer 102 may use a film, or alamination thereof, based on an element selected from Ni, Ti, W,WSi_(x), Al, Mo, Ta, Cr or Mo, or an alloy or compound material based onthe element or elements. The etching-stop layer 102 is to serve as aseed layer (cathode in a plating process) in an electrolytic platingprocess to be carried out later. Subsequently, an insulating film 101 isformed based on silicon to cover the etching-stop layer 102. (FIG. 1A)

Then, patterning is made to selectively etch the insulating film 101thereby forming an opening (trench) reaching the etching-stop layer 102.After forming a first barrier layer 103, an electrolytic plating processis carried out to form a low-resistance metal film having a sufficientthickness in the opening (trench). The electrolytic plating process is amethod to flow a direct current in a solution containing the ions of ametal to be formed by the plating process thereby forming a metal filmon a cathode surface. The plating metal can use a material having a lowelectric resistance, e.g. copper, silver, gold, chromium, iron, nickel,platinum or an alloy of these. The film thickness of a metal film to beformed in an electrolytic plating process can be properly set withcontrolling a current density and time by a practitioner. Because copperhas an extremely low electric resistance, shown herein is an exampleusing copper (Cu) that electrolytic plating is possible in forming a lowresistance metal film. Prior to plating, a seed is preferably formed.Meanwhile, the first barrier layer 103 is a diffusion preventing layeragainst copper having a fast diffusion rate in an insulating film basedon silicon oxide, i.e. a barrier metal, preferably using a metalmaterial (WN_(x), TaN_(x), TiSi_(x)N_(y), WSi_(x)N_(y), TaSi_(x)N_(y),or the like) having a specific resistance value of 300-500 μΩcm or less.Meanwhile, because copper has a poor adhesion to an insulating filmbased on silicon oxide, it is useful to form a first barrier layer 103having a good adhesion.

Then, a planarizing process is carried out, which is represented by thechemical mechanical polish process (hereinafter, referred to as CMPprocess). Due to this, the copper and first barrier layer is left onlyin the opening (trench). Unwanted parts are removed away, therebyforming a buried-type interconnection (hereinafter, referred to asburied interconnection) 104 a, 104 b (FIG. 1B)

In order to enhance the oxidation resistance of an exposed part ofcopper, a second barrier layer 106 is formed. The second barrier layer106 is useful as a diffusion preventing layer against copper having afast diffusion rate in an insulating film based on silicon oxide, andpreferably uses silicon nitride or a metal material (TiN, NbN, WN_(x),TaN_(x), TiSi_(x)N_(y), WSi_(x)N_(y), TaSi_(x)N_(y), or the like).Meanwhile, because copper has a poor adhesion to an insulating filmbased on silicon oxide, it is useful to form a second barrier layer 106having a good adhesion.

Subsequently, a layer 107 expressed by AlN_(x)O_(y) is formed as anunderlying insulating film for prevention against impurity diffusioninto a TFT to be formed later. The layer 107 expressed by AlN_(x)O_(y)may be deposited by an RF sputter technique using a target of AlN or Alwith oxygen, nitrogen or inert gas introduced from the foregoing gasintroducing system. Nitrogen may be contained in a range of several atm% or more, preferably 2.5 atm %-47.5 atm %, in the layer expressed byAlN_(x)O_(y). Oxygen may be 47.5 atm % or less, preferably 0.01-20 atm %or less.

Then, an underlying insulating film 108 is formed by a lamination ofinsulating films such as a silicon oxide film, a silicon nitride film ora silicon oxynitride film. Although the underlying insulating film 108herein uses a two-layer structure, it may use a structure having asingle layer or a two layers or more of the insulating films. The firstlayer 108 a of the underlying insulating film is a silicon oxide nitridefilm deposited to 10-200 nm (preferably 50-100 nm) by a plasma CVDprocess using a reaction gas of SiH₄, NH₃ and N₂O. Herein, formed is asilicon oxide nitride film (composition ratio: Si=32%, O=27%, N=24% andH=17%) having a film thickness of 50 nm. The second layer 108 b of theunderlying insulating film is a silicon oxide nitride film deposited to50-200 nm (preferably 100-150 nm) by a plasma CVD process using areaction gas of SiH₄ and N₂O. Herein, formed is a silicon oxide nitridefilm (composition ratio: Si=32%, O=59%, N=7% and H=2%) having a filmthickness of 100 nm. (FIG. 1C)

Subsequently, a semiconductor layer is formed on the underlying film.The semiconductor layer is formed by patterning, into a desired form, acrystalline semiconductor film obtained by forming anamorphous-structured semiconductor film by known means (sputter process,LPCVD process or plasma CVD process) and carrying out a knowncrystallizing process (laser crystallizing process, thermalcrystallizing process or thermal crystallizing process using a catalystsuch as nickel). This semiconductor layer is formed in a thickness of25-80 nm (preferably 30-60 nm). The material of the crystallinesemiconductor film, although not limited in material, is preferablyformed of silicon or a silicon-germanium alloy.

In the case of making a crystalline semiconductor film by a lasercrystallizing process, it is possible to use an excimer laser of apulse-oscillation or continuous-oscillation type, a YAG laser or a YVO₄laser. In the case of using such a laser, preferably used is a methodthat the laser light emitted from a laser oscillator is focused by anoptical system into a linear form to be irradiated onto thesemiconductor film. The condition of crystallization is to beappropriately selected by the practitioner. In the case of using anexcimer laser, pulse oscillation frequency is 30 Hz and laser energydensity is 100-400 mJ/cm² (typically 200-300 mJ/cm²). Meanwhile, in thecase of using a YAG laser, preferably its second harmonic is used andpulse oscillation frequency is 1-10 kHz and laser energy density is300-600 mJ/cm² (typically 350-500 mJ/cm²). The laser light focusedlinear to a width of 100-1000 μm, e.g. 400 μm, is irradiated throughoutthe substrate entirety, whereupon the overlap ratio of linear laser beammay be taken 80-98%.

Then, the surface of the semiconductor layer is cleaned by an etchantcontaining a hydrogen fluoride, to form a gate insulating film 109covering the semiconductor layer. The gate insulating film 109 is formedby an insulating film containing silicon having a thickness of 40-150 nmby the use of a plasma CVD process or sputter process. This embodimentforms a silicon oxide nitride film (composition ratio: Si=32%, O=59%,N=7% and H=2%) in a thickness of 115 nm by a plasma CVD process.Naturally, the gate insulating film is not limited to a silicon oxidenitride film but may be made in a single layer or a lamination of layersof insulating films containing other form of silicon.

After cleaning the surface of the gate insulating film 109, a gateelectrode 110 or connection electrode is formed. Before forming a gateelectrode 110, a contact hole is formed reaching the buriedinterconnection 104 a, 104 b. Thus, electric connection is provided byforming a gate electrode 110 contacted with the buried interconnection104 b or a connection electrode contacted with the buriedinterconnection 104 a.

Then, a p-type providing impurity element (such as B), boron herein, isadded in proper amount to the semiconductor, to form a source region 111and a drain region 112. After the addition, heating process, intenselight radiation or laser irradiation is made in order to activate theimpurity element. Simultaneously with activation, restoration ispossible from the plasma damage to the gate insulating film or from theplasma damage at the interface between the gate insulating film and thesemiconductor layer. Particularly, it is extremely effective toirradiate the second harmonic of a YAG laser at a main or back surfacethereby activating the impurity element in an atmosphere at roomtemperature to 300° C. YAG laser is preferable activating means becauseof less maintenance.

In the subsequent process, after an interlayer insulating film 113 isformed of an organic or inorganic material and hydrogenation is madethereon, a contact hole is formed therein reaching the source region,drain region or connection electrode. Next, a source electrode (line)115 and a drain electrode 114 are formed to complete a TFT (p-channelTFT) having a buried interconnection. (FIG. 1E) Although the example washerein shown that the buried interconnection and the drain electrode 114are connected together through a connection electrode simultaneouslyformed with the gate electrode, a drain electrode may be formed afterforming a contact hole reaching the buried interconnection without usinga connection electrode.

The TFT having a buried interconnection 104 a, 104 b obtained by theabove process can be used on various semiconductor devices, e.g. TFTs(current-control TFT) of a light-emitting device as shown in FIGS. 2Aand 2B, or pixel TFTs of a liquid-crystal display device as shown inFIG. 12.

Incidentally, although illustrated herein were the buriedinterconnection 104 b connected to the gate electrode and the buriedinterconnection 104 a connected to the drain electrode, the applicationis possible, without limitation, to various interconnections, e.g.source line, extended line, power supply line, capacitance line or thelike, thereby achieving resistance reduction.

Also, the invention is not limited to the TFT structure of FIG. 1E but,if required, may be in a lightly doped drain (LDD) structure having anLDD region between the channel region and the drain region (or sourceregion). This structure is provided with a region an impurity element isadded with light concentration at between the channel region and thesource or drain region formed by adding an impurity element with highconcentration, which region is called an LDD region. Furthermore, it maybe in, what is called, a GOLD (Gate-drain Overlapped LDD) structurearranging an LDD region overlapped with a gate electrode through a gateinsulating film.

Meanwhile, although explanation herein was by using the p-channel TFT,it is needless to say that a p-channel TFT can be formed by using ann-type impurity element (P, As, etc.) in place of the p-type impurityelement.

Also, although explanation herein was on a top-gate TFT, the inventionis applicable regardless of the TFT structure, e.g. the invention isapplicable to a bottom-gate TFT or a forward stagger TFT.

The invention configured above will be explained with greater detail bythe following embodiment.

EXAMPLE Example 1

This example shows that the major part of the power supply line of alight-emitting device is made as a buried interconnection, in FIGS. 3 to6.

At first, according to the above embodiment, an etching-stop layer isformed on a substrate having an insulating surface and a silicon-basedinsulating film is formed covering the etching-stop layer. Theinsulating film is selectively etched to form an opening (trench)reaching the etching-stop layer. After forming a first barrier layer,electrolytic plating is carried out to form a low-resistance metal filmhaving a sufficient thickness in the opening (trench). Subsequently,planarization represented by the chemical mechanical polishing(hereinafter, referred to as CMP) is made to leave the copper and firstbarrier layer only in the opening (trench) but remove away unwantedportions, thereby forming an interconnection in a buried form. The topview in this process stage is shown in FIG. 3, wherein the sectionalview taken along the dotted line x-x′ therein corresponds to FIG. 1C. InFIG. 3, 12 is a pixel region, 13 is a source drive circuit, and 14, 15show regions arranging gate drive circuits. As shown in FIG. 3, thepower supply line 16 has, at its end, a connection electrode padprovided in a corner of the substrate to flow a current from an externalpower source when carrying out electrolytic plating. Incidentally,because this example is made in an example having single-colorlight-emitting elements arranged in a matrix form, the pattern isconnected such that the power source line 16 is common between thepixels to make them at the same potential.

Incidentally, the power source line 16 is shown only eight in the numberfor simplification sake. In the case there are pixels in the number ofm×n (m rows by n columns), the power supply line is actually given m inthe number or the number added with one or two spare lines for enhancingthe evenness in electrolytic plating.

Then, a second barrier layer is formed in order to provide an exposedportion of copper with enhanced resistance to oxidation. Furthermore,after forming a layer represented by AlN_(x)O_(y) as an underlyinginsulating film, an underlying insulating film is formed by a laminationof insulating films such as a silicon oxide film, a silicon nitride filmor a silicon oxide nitride film. Then, a crystalline semiconductor filmis patterned to a desired form to form a semiconductor layer, followedby forming a gate insulating film covering the semiconductor layer.

After forming a contact hole reaching the buried interconnection, a gateline, a terminal electrode and an extended electrode are formed on thegate insulating film. The extended electrode, provided between thesource drive circuit 13 and the pixel region 12, is an electrodearranged such that a source line formed later is not overlapped with theextended line (line connected to a cathode or anode of thelight-emitting element) 17. Meanwhile, terminal electrodes are providedin plurality at an end of the substrate, some of which are connected tothe power supply line as buried interconnection. The top view in thisprocess stage is shown in FIG. 4.

Then, the semiconductor is properly added by a p-type providing impurityelement (B or the like) or n-type providing impurity element (P, As orthe like), to form source and drain regions. Subsequently, in order toactivate the added impurity element, heating process, intense lightradiation or laser irradiation is carried out. Then, after an interlayerinsulating film is formed and hydrogenation is made, contact holes areformed reaching the source region, the drain region, the extendedelectrode, the terminal electrode or the buried interconnection.

Subsequently, source electrodes (lines), drain electrodes or connectionelectrodes are formed to complete various TFTs. In the stage completingthe above process, in the pixel region 12, the source region and thepower supply line are electrically connected to form a connectionelectrode contacted with the drain region (not shown herein). Meanwhile,in the drive circuit, formed are a source electrode (line) contacted tothe source region and a drain electrode contacted to the drain region.Also, in the terminal region, formed are a source line connected to acertain terminal electrode and an extended line (line connected to acathode or anode of a light-emitting element) 17 connected to anotherterminal electrode. Also, between the drive circuit and the pixel regionis formed an extended line (line connected to a cathode or anode of alight-emitting element) 17. The top view in this process stage is shownin FIG. 5.

Then, in the pixel region, the first electrodes 19 are arranged in amatrix form that are connected to the connection electrode contacted tothe drain regions. The first electrodes 19 are made into anodes orcathodes of light-emitting elements. Next, formed is an insulator(called bank, partition wall or barrier wall) covering the end of thefirst electrode 19. Next, in the pixel region, a layer 10 containingorganic compound is formed, on which a second electrode 11 is formed tocomplete a light-emitting element. The second electrode 11 is made intoa cathode or anode of the light-emitting element. Incidentally, in aregion between the pixel region and the source drive circuit, the secondelectrode 11 is electrically connected to the extended line 17.

Then, the substrate and a sealing member (light-transmissive substrate,herein) 30 are bonded together by a sealant 31. The top view in thisprocess stage is shown in FIG. 6. Furthermore, in order to shield fromthe outside air, a protection film may be formed of silicon nitride,silicon oxide nitride or DLC (diamond-like carbon) on the secondelectrode 11. Finally, an FPC (flexible print circuit) for connection toan external circuit is bonded to the terminal electrode.

By the above process, completed is an active-matrix light-emittingdevice.

Incidentally, concerning the active-matrix light-emitting device havingTFTs, two constructions can be considered according to the direction oflight radiation. One is a structure that the light from thelight-emitting element is radiated through the second electrode to theeye of an observer. In this case, the observer can recognize an image onthe side of the second electrode. The other one is a structure that thelight from the light-emitting element is radiated through the firstelectrode and substrate to the eye of an observer.

In the case of the structure that the light from the light-emittingelement radiates through the second electrode to the eye of an observeras shown in FIG. 2A, it is desired to use a light-transmissive materialfor the second electrode 11 (electrode 119 in FIG. 2A).

For example, where the first electrode 19 (electrode 117 in FIG. 2A) ismade as an anode, the material of the first electrode 19 uses a metalhaving a great work function (Pt, Cr, W, Ni, Zn, Sn or In). After an endregion is covered by an insulator (called bank, partition wall orbarrier wall) 116, a poly (ethylene dioxythiophene)/poly (styrenesulfonic acid) solution (PEDOT/PSS) is applied to the entire surface andbaked. Thereafter, after a polyvinyl carbazole (PVK) solution doped withluminescent center pigment acting as a light-emitting layer (1, 1, 4,4-tetraphenyl-1, 3-buthadiene (TPB),4-dicyanomethylene-2-methyl-6-(p-dimethylamino-styryl)-4H-pyran (DCM1),Nilered, coumarine 6, or the like) is applied to the entire surface andbaked, a cathode may be formed by a second electrode 11 (electrode 119in FIG. 2A) having a lamination of a thin film containing a metal havinga small work function (Li, Mg or Cs) and a transparent conductive film(ITO (indium oxide tin oxide alloy), indium oxide zinc oxide alloy(In₂O₃—ZnO), zinc oxide (ZnO) or the like) layered thereon.Incidentally, in FIG. 2A, an auxiliary electrode 120 is provided on theinsulator 116, in order to reduce the resistance in the cathode. Thelight-emitting element thus obtained shows white light emission.Incidentally, the PEDOT/PSS, using water as solvent, is insoluble inorganic solvent. Accordingly, in the case of applying PVK thereon, thereis no fear of re-dissolution. Meanwhile, because solvent is differentbetween PEDOT/PSS and PVK, it is preferred not to use the same one inthe deposition chamber. Incidentally, although the example was hereinshown that the layer 10 containing organic compound (118 in FIG. 2A) wasformed by the application, there is no especial limitation, i.e. may beformed by a deposition process.

Meanwhile, although the above example showed the example having alamination of organic compound as shown in FIG. 7B, the organic compoundlayer can be made in a single layer as shown in FIG. 7A. For example,electron-transporting 1, 3, 4-oxadiazole derivative (PBD) may bedispersed in hole-transporting polyvinyl carbazole (PVK). Meanwhile, 30wt % of PBD is dispersed as electron-transport agent and four kinds ofpigments (TPB, coumarin 6, DCM1, nilered) are dispersed in properamount, thereby obtaining white light emission. Also, as shown in FIG.7C, the organic compound layer may be provided by a lamination of apolymer material layer and a low-molecule material layer.

Incidentally, the organic compound film is formed between the anode andthe cathode. By recombining between the holes injected at the anode andthe electrons injected at the cathode in the organic compound film,white light emission is obtained in the organic compound film.

Also, by properly selecting and superposing, for mixing colors, anorganic compound film for red light emission, an organic compound filmfor green light emission and an organic compound film for blue lightemission, it is possible to obtain white light emission in the entirety.

There are various methods of full-color displaying by the use oflight-emitting elements for white light. For example, as shown in FIG.8A, there is a method of passing obtained white light emission through acolor filter thereby obtaining red, green and blue light (hereinafter,referred to as color filter method).

By forming a color filter having a coloring layer (R) absorbing theportion other than red, a coloring layer (G) absorbing the portion otherthan green and a coloring layer (B) absorbing the portion other thanblue in a direction the organic compound film emits white light, thewhite light from the light emitting element is separated to obtain redlight, green light and blue light. Also, in the case of an active-matrixtype, the TFTs are structurally formed between the substrate and thecolor filter. Meanwhile, the color filter has shade layer between thecoloring layers. Where the screen is made great, the shade layerpreferably includes desiccant.

The coloring layer (R, G, B) can use, besides a stripe pattern in thesimplest form, an oblique mosaic arrangement, a triangular mosaicarrangement, an RGBG four-pixel arrangement or an RGBW four-pixelarrangement.

FIG. 9 shows an example of a relationship between a transmission ratioand a wavelength on each coloring layer using white light source (D65).The coloring layer constituting the color filter is formed by using acolor resist of an organic photosensitive material dispersed with apigment. Meanwhile, FIG. 10 shows, on a chromaticity coordinate, a colorreproduction range in the case of combining white emission light with acolor filter. Note that the chromaticity coordinate of white emissionlight (x, y)=(0.34, 0.35). From FIG. 10, it can be seen that colorreproduction as full colors is fully secured.

Incidentally, in this case, even if there is a difference in obtainablelight color, because each is formed by the organic compound film toexhibit white emission light, there is no need to separately applyorganic compound films for the emission light colors. Also, it ispossible to eliminate the especial need for a circular polarizationplate that prevents mirror reflection.

Now explanation is made on a CCM (color changing mediums) method to berealized by combining a blue light-emitting element having ablue-light-emitting organic compound film with a fluorescent colorchange layer, with reference to FIG. 8B.

In the CCM method, the fluorescent color change layer is excited by theblue light emitted from a blue light-emitting element, to carry outcolor change by each color change layer. Specifically, change of blue tored (B→R) is made by a color change layer, change of blue to green (B→G)is made by a color change layer and change of blue to blue (B→B). ismade by a color change layer (note that the change of from blue to bluemay be omitted), thereby obtaining light emission of red, green andblue. In also the CCM method, for the active matrix type, TFTs arestructurally formed between the substrate and the color change layer.

Incidentally, in also this case, there is no need to form organiccompound films by separate applications. Also, it is possible toeliminate the necessity of the circular polarization plate forpreventing mirror reflection.

Meanwhile, where the CCM method is used, the color change layer isexcited by external light because of its fluorescent nature, possiblyresulting in a problem of contrast reduction. It is accordinglypreferred to raise the contrast by attaching a color filter or so, asshown in FIG. 8C.

Explanation is herein made on the external appearance of theactive-matrix light-emitting device overall, in FIGS. 11A and 11B. FIG.11A is a top view showing the light-emitting device while FIG. 11B is asectional view taken along A-A′ in FIG. 11A. 901 shown by the dottedline is a source signal-line drive circuit, 902 is a pixel region, and903 is a gate signal-line drive circuit. Also, 904 is a sealingsubstrate and 905 is a sealant. The interior surrounded by the sealant905 is defined as a space 907.

908 is a line for conveying a signal to be inputted to the sourcesignal-line drive circuit 901 and gate signal-line drive circuit 903,which receives a video signal or clock signal from an FPC (flexibleprint circuit) 909 serving as an external input terminal. Although onlythe FPC is shown, the FPC may be attached with a printed wiring board(PWB). The light-emitting device, in this description, assumablyincludes, besides the light-emitting device main body, a state an FPC orPWB is attached thereon.

Explanation is now made on a sectional structure, by using FIG. 11B.Although the substrate 910 is formed thereon with a drive circuit and apixel region, the source signal-line drive circuit 901 and pixel region902 is herein shown as a drive circuit.

The source signal-line drive circuit 901 is formed with a CMOS circuitas a combination of an n-channel TFT 923 and a p-channel TFT 924. TheTFTs forming the drive circuit may be formed by a known CMOS circuit,PMOS circuit or NMOS circuit. Although this embodiment shows adriver-integrated type having a drive circuit formed on the substrate,it not necessarily required, i.e. it can be externally formed instead ofon the substrate.

The pixel region 902 is formed with a plurality of pixels each of whichincludes a switching TFT 911, a current-control TFT 912 and a firstelectrode. (anode) 913 electrically connected to the drain thereof. Thecurrent-control TFT 912 has a source electrically connected with aburied interconnection 930.

Meanwhile, an insulating layer 914 is formed at both ends of the firstelectrode (anode) 913, while a layer 915 containing organic compound isformed on the first electrode (anode) 913. Furthermore, a secondelectrode (cathode) 916 is formed on the layer 915 containing organiccompound. This forms a light-emitting element 918 comprising the firstelectrode (anode) 912, the layer 915 containing organic compound and thesecond electrode (cathode) 916. Because the light-emitting element 918herein is exemplified to emit white light, there is provided a colorfilter formed by a coloring layer 931 and a BM 932 (overcoat layer isnot shown herein for simplification sake).

The second electrode (cathode) 916 serves also as an interconnectioncommon to all the pixels, which is electrically connected to the FPC 909via the connection line 908. Also, a third electrode (auxiliaryelectrode) is formed on the insulating layer 914, thus realizing theresistance reduction in the second electrode.

The sealing substrate 904 is bonded by the sealant 905 in order to sealthe light-emitting elements 918 formed on the substrate 910. Aresin-film spacer may be provided in order to secure a spacing betweenthe sealing substrate 904 and the light-emitting element 918. An inertgas, such as nitrogen, is filled in the space 907 at the inside of thesealant 905. The sealant 905 preferably uses an epoxy resin. The sealant905 is desirably of a material less permeable of moisture or oxygen.Furthermore, a substance having an effect to absorb oxygen or moisturemay be included in the space 907.

In this embodiment, the material structuring the sealing substrate 904can use, as a material, a plastic substrate of FRP(fiberglass-reinforced plastics) PVF (polyvinyl fluoride), Mylar,polyester or acryl, besides a glass or quartz substrate. Also, after thesealing substrate 904 is bonded by using the sealant 905, it can befurther sealed in a manner covering the side surface (exposed surface)by a sealant.

By sealing the light-emitting elements in the space 907 as in the above,the light-emitting elements can be completely shielded from the outside.This can prevent a substance such as oxygen or moisture that acceleratesdeterioration of the organic compound layer from externally intruding.Accordingly, a reliable light-emitting device can be obtained.

On the other hand, in the case of the structure that the emission lightfrom the light-emitting element is radiated through the first electrodeand substrate to the eye of an observer as shown in FIG. 2B, the firstelectrode 19 (electrode 117 in FIG. 2A) desirably uses alight-transmissive material.

For example,, in the case that the first electrode 19 (electrode 117 inFIG. 2B) is an anode, the material of the first electrode 19 uses atransparent conductive film (ITO (indium oxide tin oxide alloy), indiumoxide zinc oxide alloy (In₂O₃—ZnO), zinc oxide (ZnO) or the like). Aftercovering the ends with an insulator (called bank, partition wall orbarrier wall) 116, a layer 118 containing organic compound is formed, onwhich a second electrode 11 (electrode 119 in FIG. 2B) of a metal film(an alloy such as of MgAg, MgIn, AlLi, CaF₂ or CaN, or a film formed byco-deposition of an element belonging to group 1 or 2 of the periodictable with aluminum) may be formed as a cathode. When forming a cathode,a resistance heating method due to evaporation is used. Forming may beselective by the use of an evaporation mask.

This example can be freely combined with the embodiment.

Example 2

This shows an example that the major part of a gate line of aliquid-crystal display device is made by a buried interconnection, inFIGS. 12 and 13.

At first, according to the above embodiment, an etching-stop layer isformed on a substrate having an insulating surface and a silicon-basedinsulating film is formed covering the etching-stop layer. Theinsulating film is selectively etched to form an opening (trench)reaching the etching-stop layer. After forming a first barrier layer,electrolytic plating is carried out to form a low-resistance metal filmhaving a sufficient thickness in the opening (trench). Subsequently,planarization represented by the chemical mechanical polishing(hereinafter, referred to as CMP) is made to leave the copper and firstbarrier layer only in the opening (trench) but remove away unwantedportions, thereby forming an interconnection in a buried form.

Then, a second barrier layer is formed in order to provide an exposedportion of copper with enhanced resistance to oxidation. Furthermore,after forming a layer represented by AlN_(x)O_(y) as an underlyinginsulating film, an underlying insulating film is formed by the layersof a silicon oxide film, a silicon nitride film or a silicon oxidenitride film. Then, a crystalline semiconductor film is patterned to adesired form to form a semiconductor layer, followed by forming a gateinsulating film covering the semiconductor layer.

After forming a contact hole reaching the buried interconnection, a gateelectrode and a terminal electrode are formed on the gate insulatingfilm. Incidentally, the gate electrode is connected to the buriedinterconnection to realize the resistance reduction in the gate line.Also, the terminal electrode is provided in plurality at the end of thesubstrate.

Then, the semiconductor is properly added by a p-type providing impurityelement (B or the like) or n-type providing impurity element (P, As orthe like), to form source and drain regions. Subsequently, in order toactivate the added impurity element, heating process, intense lightradiation or laser irradiation is carried out. Then, after an interlayerinsulating film is formed and hydrogenation is made, contact holes areformed reaching the source region, the drain region, and the terminalelectrode.

Subsequently, source electrodes (lines) 55 or drain electrodes areformed to complete various TFTs. In the stage completing the aboveprocess, in the pixel region 52, the drain regions and the respectivedrain electrodes are electrically connected while source regions andsource electrodes (lines) are electrically connected. Meanwhile, in thedrive circuit, formed are a source electrode (line) contacted to thesource region and a drain electrode contacted to the drain region. Also,in the terminal region, formed are a source line connected to a certainterminal electrode. Then, in the pixel region, the pixel electrodes 59are arranged in a matrix form that are contacted to the connectionelectrode contacted to the drain regions. The top view in this processstage is shown in FIG. 13. In FIG. 13, 52 is a pixel region, 53 is asource drive circuit, and 54 shows a region arranging a gate drivecircuit. As shown in FIG. 13, the gate line 56 has, at an end, aconnection electrode pad provided close to an end of the substrate toflow a current from an external power supply when carrying outelectrolytic plating. Incidentally, in this example, the connectionelectrode pads are provided corresponding to the same number of the gatelines 56. Meanwhile, the gate lines may be formed by connecting thepatterns to place all the gate lines in the same potential to carry outa plating process and then cutting them into individual gate lines.

Then, after forming an orientation film 62 a, a rubbing process iscarried out. Then, the substrate and a counter substrate 60 are bondedtogether by a sealant (not shown), to fill a liquid-crystal material 63between the substrates, followed by being sealed. The counter substrate60 is previously provided with a counter electrode 61 of a transparentconductive film and an orientation film 62 b rubbing-processed. Finally,an FPC (flexible print circuit) for connection to an external circuit isbonded to the terminal electrode. Further, a polarization plate and acolor filter are provided.

By the above process, an active-matrix liquid-crystal display device iscompleted.

Incidentally, concerning the active-matrix liquid-crystal display devicehaving TFTs, three constructions (transparent type, reflection type andsemi-transparent type) are to be considered. Although there are atransmission type having a pixel electrode made by a transparentconductive film to provide a backlight, a reflection type having a pixelelectrode made by a reflection metal film to reflect external light, anda semi-transparent type having a pixel electrode a part of which is madeby a transparent conductive film and the other part made by a reflectionmetal film to properly cause switching, the invention can be applied toany of the structures.

This example can be freely combined with the embodiment.

Example 3

The drive circuit and pixel region formed by carrying out the inventioncan complete various modules (active-matrix liquid-crystal module,active-matrix EC module). Namely, the invention can complete anelectronic apparatus built it in a display part.

Such electronic apparatuses include video cameras, digital cameras,head-mount displays (goggle type displays), car navigators, projectors,car stereo sets, personal computers, and personal digital assistants(mobile computers, cellular phones or electronic books). Examples ofthem are shown in FIGS. 14A to 14C and 15A and 15B.

FIG. 14A is a personal computer, including a main body 2001, an imageinput part 2002, a display part 2003, a keyboard 2004 and so on.

FIG. 14B is a mobile computer, including a main body 2201, a camera part2202, an image receiving part 2203, an operation switch 2204, and adisplay part 2205.

FIG. 14C is a player using a recording medium recording a program(hereinafter, referred to as recording medium), including a main body2401, a display part 2402, a speaker part 2403, a recording medium 2404,and an operation switch 2405. Incidentally, the player uses, as arecording medium, a DVD (Digital Versatile Disc), a CD or the like,enabling music listening, movie viewing or the Internet.

FIG. 15A is a portable book (electronic book), including a main body3001, a display part 3002, 3003, a storage medium 3004, an operationswitch 3005, and an antenna 3006.

FIG. 15B is a display, including a main body 3101, a support base 3102,and a display part 3103. The invention can complete a display part 3103having a diagonal length 10-50 inches.

As in the above, the invention has extremely broad application range,and can complete an electronic appliance in every field. Also, theelectronic apparatus of this example can be realized by using astructure in any of combinations of the embodiment and examples 1 and 2.

According to the present invention, in a semiconductor devicerepresented by an active-matrix light-emitting display device orliquid-crystal display device, even if the pixel region area increasesand the screen size increases, favorable display can be realized.Because the line resistance in the pixel region can be greatlydecreased, the present invention can cope with a large screen having adiagonal length of 40 or 50 inches.

1. A light-emitting device comprising: a substrate having an insulatingsurface; a second substrate having light transmission property; a pixelregion having a plurality of light-emitting elements, the light emittingelement having a first electrode, a layer containing organic compoundprovided on and in contact with the first electrode, and a secondelectrode provided on and in contact with the layer containing organiccompound; and a drive circuit having thin-film transistors, wherein thepixel region is arranged with a gate line, source line or power supplyline made with a buried interconnection.
 2. A light-emitting deviceaccording to claim 1, wherein the buried interconnection comprises atleast one material selected from the group consisting of copper, silver,gold and an alloy thereof.
 3. A light-emitting device according to claim1, wherein the buried interconnection is provided in a layer below thethin-film transistor.
 4. A light-emitting device according to claim 1,wherein the layer containing organic compound is a material for whitelight emission and combined with a color filter provided on the secondsubstrate.
 5. A light-emitting device according to claim 1, wherein thelayer containing organic compound is a material for single-color lightemission and combined with a color change layer or coloring layerprovided on the second substrate.
 6. A light-emitting device accordingto claim 1, wherein the light-emitting device is incorporated into anelectronic apparatus selected from the group consisting of a videocamera, a digital camera, a head-mount display, a car navigator, aprojector, a car stereo, a personal computer, a personal digitalassistant.
 7. A liquid-crystal display device comprising: a firstsubstrate having an insulating surface; a second substrate having lighttransmission property; a pixel region having a first electrode, a secondelectrode and a liquid-crystal material sandwiched between the first andsecond electrodes; and a drive circuit having thin-film transistors,whereby the pixel region is arranged with a gate line or source linemade with a buried interconnection.
 8. A liquid-crystal display deviceaccording to claim 7, wherein the buried interconnection comprises atleast one material selected from the group consisting of copper, silver,gold and an alloy thereof.
 9. A liquid-crystal display device accordingto claim 7, wherein the buried interconnection is provided in a layerbelow the thin-film transistor.
 10. A liquid-crystal display deviceaccording to claim 7, wherein the liquid crystal display device isincorporated into an electronic apparatus selected from the groupconsisting of a video camera, a digital camera, a head-mount display, acar navigator, a projector, a car stereo, a personal computer, apersonal digital assistant.
 11. A method for manufacturing alight-emitting device comprising: forming an etching-stop layer havingan electric conductivity on an insulating surface; forming a firstinsulating film covering the etching-stop layer; etching the firstinsulating film to open an opening reaching the etching-stop layer;forming a seed and carrying out plating to form a buried interconnectioncovering the opening; planarizing a surface of the buriedinterconnection; forming a second insulating film containing aluminum;forming a third insulating film on the second insulating film; forming asemiconductor layer on the third insulating film; forming a fourthinsulating film on the semiconductor layer; forming a gate electrode onthe fourth insulating film; forming a line connecting to thesemiconductor layer and a line connecting the buried interconnection;forming a first electrode; and forming a layer containing organiccompound on the first electrode and a second electrode on the layercontaining organic compound.
 12. A method for manufacturing alight-emitting device according to claim 11, wherein the buriedinterconnection is a power supply line.
 13. A method for manufacturing alight-emitting device according to claim 11, wherein the buriedinterconnection comprises at least one material selected from the groupconsisting of copper, silver, gold and an alloy thereof.
 14. A methodfor manufacturing a liquid-crystal display device comprising: forming anetching-stop layer having an electric conductivity on an insulatingsurface; forming a first insulating film covering the etching-stoplayer, etching the first insulating film to open an opening reaching theetching-stop layer; forming a seed and carrying out plating to form aburied interconnection covering the opening; planarizing a surface ofthe buried interconnection, forming a second insulating film containingaluminum, forming a third insulating film on the second insulating film;forming a semiconductor layer on the third insulating film; forming afourth insulating film on the semiconductor layer; forming a gateelectrode on the fourth insulating film, and forming a source lineconnected to the semiconductor layer and a line connecting between theburied interconnection and the gate line.
 15. A method for manufacturinga liquid-crystal display device according to claim 14, wherein theburied interconnection is a gate line.
 16. A method for manufacturing aliquid-crystal display device according to claim 14, wherein the buriedinterconnection comprises at least one material selected from the groupconsisting of copper, silver, gold and an alloy thereof.